The invention relates to a blank for the production of an outer sheet panel for a bodywork part, such a bodywork part, in particular a motor vehicle door, and a method for the production of such a bodywork part.
Increased demands in the protection of the occupants of motor vehicles have led to the side region of the bodywork also being more strongly protected from an impact in the event of a collision with another vehicle or with an object. Usually, so-called “side crash supports” are attached inside the vehicle doors for this purpose.
These supports usually consist of high-tensile steel, which possesses high energy absorbing capacity in the event of an impact. The protection of the vehicle occupants has been substantially improved by using such side crash supports. However, they lead to a considerable increase in the weight of the doors.
The latter is particularly disadvantageous in regard to the generally pursued weight reduction of vehicle bodies. Furthermore, the attachment of the side crash supports makes several production stages necessary, which must be carried out in addition to the other production stages during the fabrication of the bodywork. This usual fabrication of the bodywork comprises the manufacture of the inner and the outer sheet panel of the respective vehicle door in each case by cold forming a sheet metal blank, into which for example the recess needed for the window opening is moulded. Subsequently, the side crash support is attached by bonding or welding to the side of the inner sheet panel assigned to the outer sheet panel. Finally, the outer sheet panel is then placed on the inner sheet panel equipped with the side crash support and both sheet panels are connected together by crimping the boundary regions. In a comparable way, the other outer sheet panels of the bodywork in the vicinity of side bodywork parts enclosing the passenger cell can be strengthened for the event of a lateral impact.
Attempt has been made to improve the strength of motor vehicle doors by forming the outer sheet panel of the vehicle doors with an inside and an outside metal skin (DE 39 34 590 C2). The inside and the outside metal skin in this case can be formed integrally as a pressed sheet part respectively. Further improved impact protection can be achieved by profiling the inner metal skin in the course of its fabrication in such a way that in the impact-endangered region of the doors it forms a side crash support, which then lies against the outer skin. As the result of such a double-skinned structure stiffening of the vehicle doors can be achieved. The expenditure necessary for the production of such doors, however, is substantial. Added to this is the fact that whenever the inner skin also comprises the side crash support, the strength of this side crash support is restricted by the demands, which are imposed with regard to the ductility of the sheet metal used for fabricating the internal skin. Also the expenditure linked with the fabrication of the vehicle doors known from DE 39 34 590 C2 is therefore substantial.